Abstract: A motor and a method of operating the motor are described. The motor may have a female rotor shaft having mounted thereon a female compression rotor, a female power rotor, and a spur gear. The motor may also have a male rotor shaft having mounted thereon a male compression rotor, a male power rotor and a power rotor gear. A housing containing the foregoing may have a front housing plate, a compression rotor case, an isolator plate, a power rotor case, a rear housing plate, and a gear cover adjacent the rear housing plate. The various female and male rotors are engaged with one another within the housing.

Abstract: A screw vacuum pump includes a gas working chamber formed by a male screw rotor and a female screw rotor respectively including unequal lead screws engaging each other and having a lead angle that continuously changes with the advance of helix and a stator receiving therein both rotors. The stator is provided with a gas inlet port and a gas outlet port that can communicate with one end portion and the other end portion of the working chamber, respectively. The male screw rotor and the female screw rotor have unequal lead screws each of which is formed into a perpendicular-to-axis cross-sectional shape that changes following a continuous change in lead angle with the advance of helix. Alternatively, one of the male screw rotor and the female screw rotor has the unequal lead screw formed into a perpendicular-to-axis cross-sectional shape that is constant. Another has the unequal lead screw formed into a perpendicular-to-axis cross-sectional shape that changes.

Abstract: A complex dry vacuum pump including a root rotor and a screw rotor is disclosed for manufacturing semiconductors and/or displays in a vacuum state in a process chamber, and discharging gaseous material and/or by-products generated during manufacturing to the exterior of the process chamber. The pump can provide high gas compression transfer efficiency so as to form a vacuum in the process chamber and/or keep high gas compression transfer efficiency when the gaseous material and/or by-products are discharged. Balance between the root rotor and the screw rotor can prevent vibration and noise generated in the vacuum pump, and molding material associated with the pump may allow a stator coil to be separated and prevent various by-products from flowing from the vacuum pump.

Abstract: A method of pumping a gas stream containing a condensable species and a light gas and an apparatus therefore, the method comprising the steps of conveying the gas stream to a multistage vacuum pump comprising an inlet stage and an exhaust stage downstream from the inlet stage, and adding to the gas stream upstream of or at the inlet stage a purge gas heavier than said light gas to both inhibit migration of the light gas from the exhaust stage towards the inlet stage and to inhibit condensation of the condensable species within the pump.

Abstract: The invention relates to a multi step helical screw compressor unit which consists of a drive housing (90), wherein a first, second, and third helical screw compressor (60, 70, 80) are secured in a protruding manner parallel to each other and are driven together by a drive toothed wheel in the drive housing. A gas-like fluid is compressed by the first helical screw compressor (60) at a first intermediate pressure of approximately 3.5 bars, by the second helical screw compressor (70) at a second intermediate pressure of approximately 12 bars and by the third helical screw compressor (80) at an end pressure of approximately 40 bars. The driven toothed wheels (65, 75) of the first and the second helical screw compressors are in contact with the drive toothed wheel (95) above the axes thereof, when the driven toothed wheel (85) of the third helical screw compressor (80) is in contact with the drive toothed wheel (95) in the vicinity of the deepest point thereof (T).

Abstract: A lubricating pump having a first stage and a second stage; the first stage in turn has an intake connectable hydraulically to a tank of lubricating fluid, and a delivery outlet connectable hydraulically to a lubricated member; the first stage compresses the lubricating fluid from the tank to a pressure for supply to the member; the second stage in turn has an inlet connectable hydraulically to a casing housing the member, and an outlet connectable hydraulically to the tank; the second stage feeds the lubricating fluid in the casing back into the tank; the second stage is a Roots type, and has a first and a second rotor rotating about respective axes to feed the lubricating fluid from the inlet to the outlet; and the first and second rotor are operated by the first stage.

Abstract: An oil pump for an internal combustion engine for drawing up the lubricating oil situated in an oil collector device has an oil pump housing wherein at least two pairs of gears are disposed. The pairs of gears, in order to form the pumping stages, are connected on the suction side to a suction passage formed in the oil pump housing and on the delivery side to a delivery passage. The oil pump housing is further formed with an oil supply passage that is connected to the suction passage of a first pumping stage and via which lubricating oil can be delivered to the suction side of the first pumping stage.

Abstract: A circular, reversible steam powered engine configured to force pistons mounted in circular housing assembly and coupled to a main shaft to create a work load. The steam powered engine is arranged to pipe steam of a high pressure into steam chambers to force pistons forward and push exhaust steam of a low pressure out of steam chambers. Gears rotate and engage with pistons to start and stop steam flow into timing valves and steam flow portions. The engine creates a torque required to effectively operate many types of loads, such as those for vehicle and equipment applications.

Abstract: A screw compressor comprising: a low pressure stage compressor body; a high pressure stage compressor body that further compresses a compressed air compressed by the low pressure stage compressor body; pinion gears for example, respectively, provided on, for example, a male rotor of the low pressure stage compressor body and, for example, a male rotor of the high pressure stage compressor body; a motor; a bull gear for example, provided on a rotating shaft of the motor; and an intermediate shaft supported rotatably and provided with a pinion gear, which meshes with the bull gear, and a bull gear, which meshes with the pinion gears. Thereby, it is possible to make the motor relatively low in rotating speed while inhibiting the gears from being increased in diameter, thus enabling achieving reduction in cost.

Abstract: An oil pump for an internal combustion engine for drawing up the lubricating oil situated in an oil collector device has an oil pump housing wherein at least two pairs of gears are disposed. The pairs of gears, in order to form the pumping stages, are connected on the suction side to a suction passage formed in the oil pump housing and on the delivery side to a delivery passage. The oil pump housing is further formed with an oil supply passage that is connected to the suction passage of a first pumping stage and via which lubricating oil can be delivered to the suction side of the first pumping stage.

Abstract: A screw pump includes a housing and a pair of intermeshing screw rotors. An end face of the rotor adjacent to an inlet port of the housing is provided with an inlet opening. Each rotor has a first portion whose lead angle changes. The first portions and the housing cooperate to form an inlet space. During rotation of the rotors, communication between the inlet space and the inlet port is blocked by the first portions and the housing thereby to form a closed pump space adjacent to the inlet space. Volume of the pump space is set smaller than the maximum volume of the inlet space. A closure member is provided which covers at least a part of the inlet openings. The closure member closes the inlet space when the volume of the inlet space exceeds that of the pump space.

Abstract: The invention reduces power consumption and makes a rotor with ease. As illustrated in FIG. 2, a multistage roots pump (1) in the invention includes upstream rotors (R1a, R1b, R2a, R2b) having multiple teeth, supported by a pair of revolving shafts (A1, A2); and downstream rotors (R3a, R3b-R5a, R5b) having an identical number of teeth (31) with the upstream rotors, supported by revolving shafts (A1, A2). The discharge area formed by the outer periphery of the downstream rotors (R3a, R3b-R5a, R5b) and the inner periphewy of the pump chambers (P1-P5) is smaller than that of the upstream rotors (R1a, R1b, R2a, R2b).

Abstract: A screw pump includes a housing and a pair of intermeshing screw rotors. The housing has an inlet port and an outlet port. Each rotor has a first portion whose lead angle decreases. The first portion and the housing form an inlet space and a pump space. Winding angle of the first portion has a first region and a second region. The first region is located in a predetermined range from the end on the first portion adjacent to the inlet port toward the outlet port. The second region is located adjacent to the first region. Reduction rate of the lead angle of the first portion in the first region is set smaller than that in the second region. The maximum lead angle of the first portion is set smaller than a lead angle which decreases at a constant rate in the first region and the second region.

Abstract: A screw compressor with two rotors held in a rotor housing has sealing arrangements 11, 11? to seal the pressurized side shaft pin of the rotors, wherein each sealing arrangement has a number of successive radial seal rings 11a, 11b and wherein it contains an annular relief chamber 51 at an intermediate position that is connected by means of a vent channel 53 to a chamber in the rotor housing in which a pressure is present that is higher than atmospheric pressure. It is preferred that the vent channel be connected to the intake chamber 10 of the rotor housing 1 and that this intake chamber be fed by a gas that is pre-compressed by a compressor stage.

Abstract: The compressor unit having at least two compressors, for example a low pressure stage compressor 11 and a high pressure stage compressor 12 connected in series, of which the low pressure sage compressor 11 and high pressure stage compressor 12 are driven by driving devices 13 and 14 respectively separately or driven by a single driving device 41 via variable speed gears 43 and 44 respectively connected to each of the compressors, and rotation speed of the low pressure stage compressor 11 and that of the high pressure stage compressor 12 are controlled independently in accordance with various operating conditions of the compressor unit so that optimal load balancing of the compressors 11 and 12 is always achieved.

Abstract: An object of this invention is to provide a vacuum apparatus used in the field of semiconductor production and capable of suppressing power consumption. The vacuum apparatus comprises vacuum containers (10, 11, 12, 13, 14, and 15) having gas inlets and gas outlets, vacuum pumps of at least one stage for depressurizing the inside of the vacuum containers or maintaining the inside of the container in a depressurized state, and compressors (4c, 5c, 6c, 7c, 8c, and 9c) connected to the discharge ports of the vacuum pumps (4b, 5b, 6b, 7b, 8b, and 9b) on the last stage among the vacuum pumps and having capacities having capability of depressurizing the input sides thereof.

Abstract: An object is to provide a high inner pressure type multistage compression rotary compressor capable of avoiding beforehand generation of vane fly of a second rotary compression element and realizing a stabilized operation, the rotary compressor includes a communication path which connects an intermediate pressure region to a region having a low pressure as a suction pressure of a first rotary compression element; and a valve device which opens or closes this communication path, the rotary compressor applies a high pressure as a back pressure of an upper vane, and this valve device opens the communication path in a case where a pressure difference between the intermediate pressure and the low pressure increases a predetermined upper limit value before the intermediate pressure reaches the high pressure.

Abstract: A composite fluid machine has a first and a second fluid delivering mechanisms. The first fluid delivering mechanism includes an accommodation chamber, a movable body, and a suction space. The movable body is accommodated in the accommodation chamber.. The suction space is defined by the accommodation chamber and the movable body. The suction space is connected to the inlet, and the flow rate of the fluid introduced into the suction space is displaced. The movable body performs a suction movement and a discharge movement.. The second fluid delivering mechanism is combined with the first fluid delivering mechanism and is located upstream of the first fluid delivering mechanism to deliver the fluid to the suction space of the first fluid delivering mechanism.. Lobes of helical roots rotors are twisted in a respective direction around the rotational axis.

Abstract: A blending pump assembly for accurately maintaining the proper ratio of two fluid components. Flow of a first fluid is utilized to drive a fluid motor, which in turn drives a pumping mechanism to inject a proportional amount of a second fluid into the flow of the first fluid. The fluid motor and pump are sized so that a predetermined ratio between the two fluids is maintained regardless of changes in pressure and flow rate of such first fluid.

Abstract: Pairs of rotors (R1, R2, R3, R4, R5 and R6) driven rotationally by a motor (22) are disposed in the body (21) of a main pump (20) comprising a multistage Roots dry vacuum pump. A suction opening (23) communicating with the rotor chamber of the rotor R1 is provided in the upper wall portion at the left end of the body (21). A delivery section (24) communicating with the delivery side of the rotor chamber of rotor R6 on the final stage is coupled to an exhaust pipe (25) and is provided with a silencer (26) and further coupled to a check valve (28) through a pipe (27). The check valve (28) has its forward direction toward the atmospheric side. The delivery section (24), or a delivery section (24?) at the side intermediate stage, is coupled to an auxiliary pump (30) having an exhaust capacity smaller than that of the main pump (20).

Abstract: A motor-pump unit is provided that has at least two internal gearwheel pumps axially aligned that are driven off of the rotor of the electric motor. The rotor of the electric motor is U-shaped and is concentrically disposed about the pump. The web of the U-shape is disposed in the region of the rotational axis with internal toothing that meshes with pinions of the at least two internal gearwheel pumps.

Abstract: In an embodiment, a vacuum pump is capable of preventing adhesion of by-products to its surfaces. The vacuum pump includes a stator. The stator includes a cylinder wall and a pair of diaphragms disposed at opposite ends of the stator. A rotary shaft passes through the diaphragms, and a lobe is attached to the rotary shaft in the stator. The lobe may include a fluid port, and the fluid port may be disposed in sidewalls of the lobe to face the diaphragms. The rotary shaft may include a fluid supply path in communication with the fluid port.

Abstract: A multi-stage vacuum pump includes a plurality of casings connected in series and each casing defining a respective compression chamber, a plurality of partition plates each set in between each two casings. When compressed by rotors at shafts in one compression chamber, compressed air passes through the air path formed in the corresponding partition plate to the next compression chamber for further compression, and finally compressed air passes to the last compression chamber through the air path formed in the last partition plate. Because the invention is designed to let compressed air directly pass through the air path in each partition plate, the outer diameter and volume of the multi-stage vacuum pump can be minimized to reduce the weight and the manufacturing cost.

Abstract: A seal assembly for the protection of a static seal device for use in a vacuum pump. The seal assembly comprising at least two components which are sealingly connected together, an o-ring seal, which is engaged between the two components to prevent transfer of fluid to and from the pump between these two components and a fluid channel. The fluid channel being in the plane of the o-ring and located between the o-ring seal and a process gas flow path. The fluid channel provides a path for a barrier gas to be routed when the apparatus is in use. The channel being connectable to an external source of barrier fluid and having an outlet in fluid communication with the pump swept volume.

Abstract: A blending pump assembly for accurately maintaining the proper ratio of two fluid components. Flow of a first fluid is utilized to drive a fluid motor, which in turn drives a pumping mechanism to inject a proportional amount of a second fluid into the flow of the first fluid. The fluid motor and pump are sized so that a predetermined ratio between the two fluids is maintained regardless of changes in pressure and flow rate of such first fluid.

Abstract: A roots pump has a housing, a plurality of rotary shafts, a rotor, a confluent passage and a closed space. The housing forms therein a pump chamber. The rotary shafts are supported on the housing in parallel relation to each other. The rotor is mounted on each of the rotary shafts, and the rotors on any adjacent rotary shafts are in engagement with each other. A set of the engaged rotors is accommodated in the pump chamber. The confluent passage is formed along one crossing line of paired imaginary swept peripheral surfaces in one-to-one correspondence with the paired and engaged rotors. The closed space is formed in one-to-one correspondence with each of the paired rotors between the paired rotors and paired peripheral wall surfaces which form the pump chamber. The closed space initially joins the confluent passage from a terminal end thereof with rotation of the paired rotors.

Abstract: A method of adapting a downhole multi-phase twin screw pump (10) for use in wells having a high gas content. A first step involves positioning a supplementary liquid channel (22,122) in a housing (12) of the pump in fluid communication with a pumping screw near an intake end (14) of the pump. A second step involves feeding supplementary liquid through the supplementary liquid channel to the pumping screw, thereby enhancing a liquid seal around the pumping screw.

Abstract: A vacuum pump includes an inlet port (14) and an exhaust port (86, 88). Gas from an enclosure connected to the inlet port is pumped to the exhaust port by first and second rotors (18, 52, 254) which are mounted on first and second shafts (30, 60) extending through a pump chamber (112). The rotors are connected with shaft sections (140, 150, 240, 250) which include a lobe (142, 172, 242, 242?) extending from the shaft sections and a mating channel (152, 182, 252, 252?) defined in the other. The lobes matingly engage the channels during rotation of the rotors to form a suction section (154). The suction section (154) compresses a volume of gas entering the pump from the inlet port (14) reducing the power consumed to move the volume of gas through the pump chamber more easily and increase pump efficiency.

Abstract: A dual gear, single outlet material pump includes a base plate, a lower gear plate and two associated gears, a spacer plate, an idler shaft, a drive shaft, an upper drive gear, and an upper gear plate. An upper idler gear is housed within a tri-lobed aperture of an upper gear plate. A plurality of screw holes are through a top plate. A plurality of heating plates are coupled to the sides of the assembled pump and a plurality of temperature sensors are coupled to the recesses in the spacer plate. An outlet manifold couples with each of the outlets of the lower gear plate and the upper gear plate to form a single outlet. The method of construction produces an easily disassembled, cleaned, and re-assembled pump.

Abstract: According to one embodiment of the invention, a gerotor apparatus includes an outer gerotor having an outer gerotor chamber, an inner gerotor, at least a portion of which is disposed within the outer gerotor chamber, and a synchronizing apparatus operable to control the rotation of the inner gerotor relative to the outer gerotor. The inner gerotor includes one or more entrance passages operable to communicate a lubricant into the outer gerotor chamber.

Abstract: A two-stage screw compressor has two compressor stages whose rotor housings are arranged with their axes parallel to one another and are enclosed by a common coolant housing at a distance. A coolant inlet and a coolant outlet are located at the common coolant housing, as well as guide walls such that the coolant flowing through the coolant housing flows around and cools the rotor housings of the two compressor stages one after the other in an S-shaped flow path.

Abstract: A roots pump has a housing, a plurality of rotary shafts, a rotor, a confluent passage and a closed space. The housing forms therein a pump chamber. The rotary shafts are supported on the housing in parallel relation to each other. The rotor is mounted on each of the rotary shafts, and the rotors on any adjacent rotary shafts are in engagement with each other. A set of the engaged rotors is accommodated in the pump chamber. The confluent passage is formed along one crossing line of paired imaginary swept peripheral surfaces in one-to-one correspondence with the paired and engaged rotors. The closed space is formed in one-to-one correspondence with each of the paired rotors between the paired rotors and paired peripheral wall surfaces which form the pump chamber. The closed space initially joins the confluent passage from a terminal end thereof with rotation of the paired rotors.

Abstract: The present invention provides a multi-stage vacuum pump which includes: a housing in which a plurality of pumping chambers are formed, the pumping chambers being arranged in series and being in fluid communication with one another, one of the pumping chambers which is at one end of the series acting as an initial stage pumping chamber, another of the pumping chamber which is at the other end of the series acting as a final stage pumping chamber, the housing being provided with an inlet port for sucking a gas from a space to be evacuated into the initial stage pumping chamber, the housing being provided with an outlet port for exhausting the gas from the final stage pumping chamber; a Roots-type pump section occupying each of the pumping chambers; and a device for decreasing a temperature differential between the initial stage pumping chamber and the final stage pumping chamber.

Abstract: Rotary piston machine for compressible media, with rotary pistons sealed tight in a common housing and rotatable with one another in a controlled manner, the rotary pistons having a plurality of disk-shaped sections engaging in one another in pairs, whose thickness and/or diameter decreases in the direction of the pressure side, each disk having a surface area and a core area connected respectively by an interface area, the sector angles of the surface area and of the core area of a respective disk not being identical, the disks having various transverse profile contours periodically recurring along the piston axes and each disk being offset at an angle to the two adjacent disks of the same rotor in a such a way that these three disks have a common area section and form a chamber.

Abstract: A multi-stage internal gear fuel pump for a vehicle includes a housing having an inlet and an outlet and a motor disposed in the housing. The multi-stage internal gear fuel pump also includes a shaft extending axially and disposed in the housing for rotation by the motor. The multi-stage internal gear fuel pump further includes a plurality of pumping modules disposed axially along the shaft and each having an internal gear and an external gear cooperating with each other for rotation by the motor to pump fuel from the inlet to the outlet.

Abstract: A two-stage screw compressor has two compressor stages whose rotor housings are arranged with their axes parallel to one another and are enclosed by a common coolant housing at a distance. A coolant inlet and a coolant outlet are located at the common coolant housing, as well as guide walls such that the coolant flowing through the coolant housing flows around and cools the rotor housings of the two compressor stages one after the other in an S-shaped flow path.

Abstract: The twin screw rotors for axis-parallel installation in displacement machines for compressible media have asymmetrical transverse profiles and numbers of wraps that are ≧2. Depending upon the wrapping angle (&agr;), the pitch (L) varies, which pitch increases in a first subdivision (T1) from the suction-side screw end, reaches a maximal value (Lmax) after one wrap, decreases in a second subdivision (T2) until a minimal value (Lmin), and is constant in a third subdivision (T3). The pitch course in the first subdivision (T1) is preferably mirror-symmetrical to that in the second subdivision (T2), within the subdivisions T1 to T2, it is point-symmetrical to the mean values in almost all cases. Compact screw rotors, completely free of imbalance, can thereby be achieved with compression rates of 1.0 . . . 10.0, also without profile variation.

Abstract: An industrial robot including a manipulator having a control system. The manipulator includes a common gear housing having first and second inner compartments connected with a passage channel. First and second gears are arranged in the first and second inner compartments and are adapted to move the manipulator. A cooling and lubricant medium is disposed in the common gear housing and circulates between the first and second inner compartments through the passage channel.

Abstract: The present invention provides a multi-stage vacuum pump which includes: a housing in which a plurality of pumping chambers are formed, the pumping chambers being arranged in series and being in fluid communication with one another, one of the pumping chambers which is at one end of the series acting as an initial stage pumping chamber, another of the pumping chamber which is at the other end of the series acting as a final stage pumping chamber, the housing being provided with an inlet port for sucking a gas from a space to be evacuated into the initial stage pumping chamber, the housing being provided with an outlet port for exhausting the gas from the final stage pumping chamber; Roots-type pump sections occupying the respective pumping chambers, each of the Roots-type pump sections having a pair of intermeshed Roots-type profile rotors; and a pair of shafts adapted for rotation within the housing about their lengthwise axes in contra-rotational direction, the pair of shafts being secured to the respective

Abstract: A package-type screw compressor includes a low-pressure stage state compressor and a high-pressure stage compressor. Motive power is transmitted from an electric motor to the two compressors via a speed increaser. The discharge gas, compressed and heated to a high temperature by the low-pressure stage compressor, is cooled by an intercooler. The discharge gas, compressed and heated to a high temperature by the high-pressure stage compressor, is cooled by an aftercooler. A casing of the intercooler and that of the aftercooler are formed integrally with a speed increaser casing, reducing the number of component parts. A cooler portion, formed by the intercooler and the aftercooler, is spaced from the speed increaser casing, thereby preventing heat, produced by the compressed air, from being transmitted to the speed increaser casing.

Abstract: A vacuum pump having a screw mechanism and comprising two externally threaded rotors mounted on respective shafts in a pump body and adapted for counter-rotation therein with intermeshing of the rotor threads with close tolerances between the threads and internal surfaces of the pump body in order that gas may be pumped from a pump inlet to a pump outlet by action of the rotor threads, the root diameter of each rotor increases and the thread diameter of each rotor decreases in a direction from the pump inlet to the pump outlet, and wherein the pitch of the rotor threads decreases in a direction from the pump inlet to the pump outlet.

Abstract: A pump comprises multiple, axially stacked positive displacement fluid device sections, such as circumferential piston pumps having chambers and contra-rotating chambers. The device can be similarly employed as a fluid motor. The stacked sections are arranged within an outer retaining barrel in one or more stages. The pump is particularly suitable for installation downhole in the casing of a wellbore. Each section comprises a pair of rotors fit to shafts which are rotatably supported on hard faced bearings between the shafts and the bosses. Each pump section draws fluid from an inlet port and discharges fluid to a common and contiguous discharge manifold. The inlets of the pump sections for a suction stage communicate with a fluid source. Cross-over sections route fluid between stages. Successive pressure stages draw fluid from the cross-over fit to the preceding stage's discharge manifold.

Abstract: The present invention relates to a compressor and method for operating a compressor comprising a first stage comprising a first stage bypass cavity and a first stage outlet, an intercooling zone in communication with said first stage outlet, a second stage comprising a second stage inlet and a second stage outlet in communication with said intercooling zone, a gearbox disposed proximate to the first stage outlet and the second stage inlet, wherein both stages communicate with the gearbox through their respective rotor shafts, a valve, wherein the valve provides means for communications between the first stage bypass cavity and the second stage during unloaded conditions, and intercooling means operable for injecting cooling fluid into the intercooling zone.

Abstract: A pump comprises multiple, axially stacked positive displacement fluid device sections, such as circumferential piston pumps having chambers and contra-rotating chambers. The device can be similarly employed as a fluid motor. The stacked sections are arranged within an outer retaining barrel in one or more stages. The pump is particularly suitable for installation downhole in the casing of a wellbore. Each section comprises a pair of rotors fit to shafts which are rotatably supported on hard faced bearings between the shafts and the bosses. Each pump section draws fluid from an inlet port and discharges fluid to a common and contiguous discharge manifold. The inlets of the pump sections for a suction stage communicate with a fluid source. Cross-over sections route fluid between stages. Successive pressure stages draw fluid from the cross-over fit to the preceding stage's discharge manifold.

Abstract: A screw-type dry vacuum pump comprises a rotor having a screw thread thereon for exhausting a gas through rotation, a casing for housing the rotor therein, a reduced portion provided in the casing, and an enlarged portion provided on a discharge end of the casing. The reduced portion forms a slight gap between the outer circumferential surface of the rotor and the inner surface thereof. The enlarged portion forms a larger gap between the outer circumferential surface of the rotor and the inner surface thereof.

Abstract: The twin screw rotors for axis-parallel installation in displacement machines for compressible media have asymmetrical transverse profiles and numbers of wraps that are ≧2. Depending upon the wrapping angle (&agr;), the pitch (L) varies, which pitch increases in a first subdivision (T1) from the suction-side screw end, reaches a maximal value (Lmax) after one wrap, decreases in a second subdivision (T2) until a minimal value (Lmin), and is constant in a third subdivision (T3). The pitch course in the first subdivision (T1) is preferably mirror-symmetrical to that in the second subdivision (T2), within the subdivisions T1 to T2, it is point-symmetrical to the mean values in almost all cases. Compact screw rotors, completely free of imbalance, can thereby be achieved with compression rates of 1.0 . . . 10.0, also without profile variation.

Abstract: The present invention provides a multi-stage vacuum pump which includes: a housing in which a plurality of pumping chambers are formed, the pumping chambers being arranged in series and being in fluid communication with one another, one of the pumping chambers which is at one end of the series acting as an initial stage pumping chamber, another of the pumping chamber which is at the other end of the series acting as a final stage pumping chamber, the housing being provided with an inlet port for sucking a gas from a space to be evacuated into the initial stage pumping chamber, the housing being provided with an outlet port for exhausting the gas from the final stage pumping chamber; Roots-type pump sections occupying the respective pumping chambers, each of the Roots-type pump sections having a pair of intermeshed Roots-type profile rotors; and a pair of shafts adapted for rotation within the housing about their lengthwise axes in contra-rotational direction, the pair of shafts being secured to the respective

Abstract: A package-type screw compressor includes a low-pressure stage state compressor and a high-pressure stage compressor. Motive power is transmitted from an electric motor to the two compressors via a speed increaser. The discharge gas, compressed and heated to a high temperature by the low-pressure stage compressor, is cooled by an intercooler. The discharge gas, compressed and heated to a high temperature by the high-pressure stage compressor, is cooled by an aftercooler. A casing of the intercooler and that of the aftercooler are formed integrally with a speed increaser casing, reducing the number of component parts. A cooler portion, formed by the intercooler and the aftercooler, is spaced from the speed increaser casing, thereby preventing heat, produced by the compressed air, from being transmitted to the speed increaser casing.

Abstract: The invention concerns a vacuum pump consisting in the assembly of two stator half-shells (101, 102) and two directly mounted end parts (31, 32) with an interposed single-piece continuous pressure seal (33). The pressure seal (33) comprises two annular end parts (34, 35) generally parallel to each other and connected by two side-members (36, 37) which are generally perpendicular thereto. Thus, the number of components to be assembled to produce an multistage dry vacuum pump is reduced, while providing satisfactory impermeability to outside atmosphere.

Abstract: In an oil-free type screw compressor including a low-pressure-stage compressor main body and a high-pressure-stage compressor main body, when the power of an motor is transmitted to an oil pump via a gear to start the pump, the lubrication oil stored in an oil sump formed at the bottom of a gear casing flows through an oil strainer. A part of the oil is introduced to an oil cooler, while the rest is introduced to a junction portion by bypassing the oil cooler. Further, a part of the oil introduced to the oil cooler is directed to the junction portion. After adjusting the temperature of the oil appropriately, it is introduced to a lubrication portion of the compressor, while the oil cooled by the oil cooler using the full capacity thereof is introduced to oil jackets of the compressor main bodies via different passages.